1. Field of the Invention
The present invention relates to a data transmitting method, a data transmitting system, a data receiving method and a receiving terminal, and more particularly, is suitably applied to a digital satellite broadcasting system.
2. Description of the Related Art
In the digital satellite broadcasting system, a broadcasting service using a communication satellite (CS) (hereinafter, this is referred to as CS broadcasting) provides user programs on hundreds of channels. Moreover, in recent years, in the CS broadcasting of the digital satellite broadcasting system, a data broadcasting service has been provided, so that the users can receive the data broadcast via a receiving board for data broadcasting.
As shown in FIG. 1, in a digital satellite broadcasting system 80, a broadcast wave transmitted from the antenna 81 of a broadcasting station is distributed via a communication satellite 82, received by an integrated receiver decoder (IRD) and a receiving board for data broadcasting (not shown in Fig.) via each antenna 83A to 85A. This received data is transmitted to each client personal computer (hereinafter, these are referred to as a client PC) 83 to 85 as a data broadcast signal. This is known as one-to-many broadcasting service that means there are many unspecified clients as receivers with respect to one broadcasting station as a sender.
Such a digital satellite broadcasting system 80 provides the one-to-many broadcasting service, so that data is not transmitted only to specified client PCs 83 to 85 from the broadcasting station.
On the other hand, in an information transmitting system using an open-network on Internet, when a client requests a server for transferring, for example, a homepage through a terrestrial circuit and Internet, the server reads the desired homepage from a prescribed database, and transmits this to the client through the same terrestrial circuit as that used when the request was made.
In such an information transmitting system using Internet, the amount of transmittable data is limited depending on a transmission rate of a telephone line that connects the server to the clients, and the traffic (data traffic). This is because it takes a long time to transmit a homepage including picture data, which has a large amount of information, from the server to the client.
To obviate such defects, in recent years, a new information transmitting system (hereinafter, this is referred to as satellite Internet system) called satellite Internet has been provided, in which a mass of data such as a homepage including picture data is distributed from a server to a client in a short time via a communication satellite for CS broadcasting.
In a satellite Internet system 90, as shown in FIG. 2 in which the same reference numerals are added to corresponding parts in FIG. 1, when a client PC 83 as a receiver requests an Internet provider (hereinafter, this is simply referred to as a provider) as a sender for transferring a desired homepage, through a public circuit 86, the sender transmits the video data of the specified homepage on an Internet 88 via an antenna 81 and a communication satellite 82, and the receiver receives the data with an IRD and a receiving board only for satellite Internet (not shown) via an antenna 83A to transmit this to the client PC 83.
This satellite Internet system 90 uses the terrestrial public circuit 86 as an up-circuit from the client PC 83, and uses a satellite circuit capable of transmitting a mass of data at a high speed as a down-circuit. Thereby, a mass of data such as a homepage including picture data can be transmitted to the client PC 83 in a short time.
Here, the satellite Internet system 90 utilizes a transmission control protocol/Internet protocol (TCP/IP) in the Internet. When a receiving board only for satellite Internet that is to receive data such as a homepage transmitted from the communication satellite 82 is installed in the IRD with plug-and-play, the satellite Internet system 90 recognizes the receiving board as a device for the network.
That is, each receiving board only for satellite Internet has a unique MAC address (media access control). The provider 87 as a sender can transmit data to the client PC 83 as a receiver via the receiving board only for satellite Internet with an IP address when the MAC address is added to the header of an Internet protocol (IP) packet.
Here, the IP address is a unique address which is composed of a network address and a host address in a network layer of the time when an IP packet is transmitted and received. The MAC address is a unique physical address which is used to identify a terminal connected to a local area network (LAN). That is, the IP packet is transmitted to a specified client based on both the IP address and the MAC address.
Then, it is considered that if the digital satellite broadcasting system 80 can utilize the communication system of the satellite Internet system 90 which realizes a one-to-one intercommunication, the one-to-one intercommunication can be realized also in the digital satellite broadcasting system 80.
However, since a digital satellite broadcasting system 80 provides a one-to-many broadcasting service, it is necessary to assign a unique MAC address to each receiving board for data broadcasting to transmit data from a broadcasting station only to specified client PCs 83 to 85.
In the digital satellite broadcasting system 80, however, the data broadcasting service using the CS broadcasting has already been implemented. Thus, it has been practically difficult to load later read only memories (ROMs) each storing a MAC address, in the receiving boards for data broadcasting that many users already have, because a recall of the receiving boards for data broadcasting is needed.